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APPLICATION BRIEF
AP-4do
October 1988
ISDN Applications with 29C53 and 80188
HERBERT WEBER TELECOM OPERATIONS
Order Number: 270247-003 5-92
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TERMINAL ADAPTOR (TA) A terminal adaptor, or "TA", is the link between existing non-ISDN equipment like terminals, facsimile, printers and the ISDN network. The (unction of this application is to effectively replace equipment such as a modem. Usually provided as a separate box, it processes RS232 or X.21 data and places it on the 4 wire'S' loop. No change at the terminal is required to make it ISDN compatible.
• Upper portion of link access procedure (CCITT 1.440) handling: - Multiple logic channels - Sequence control - Error correction (retransmission) - Flow control
The design is based on a 29C53 transceiver for the ISDN connection and an 80188 microprocessor in combination with an 82530 communications controller for the data connection. Benefits of the application are: • Data rates up to 19.2 Kb!s using an RS232 interface or up to 48 Kb!s using an X.21 interface. • Compact design and low cost. • Virtually error free transmission.
EPLD • Interface conversion,' serial to!from SLD • B-channel assignment
29C53 • Physical level interface (CCITT 1.430) • Lower portion of the link access procedure: - Zero insertion!deletion - CRC generation and checking - Flag appending and detection • D-channel message buffering
Link Setup The user sets up a call in the same manner as a Hayes· modem user does, i.e. a command is transferred to the adaptor via the RS232 interface. The command takes the form of an ASCII string in which the first 2 characters are "AT".
The 80188 passes the information for the D-channel messages via the parallel bus into the FIFO's of the 29C53.
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The 80188 accepts the command and begins the call setup procedure by communicating the call's destination to the NT (or CO). This is achieved by passing call setup messages to a link level protocol, which is passed to the NT over the physical level (S bus). The partitioning of the tasks is as follows:
The NT grants a B-channel (if available) to the TA and the channel is now ready for data transfer.
Data Transfer An indication is given to the user's terminal via the RS232 or X.21 port that communication may commence. Any subsequent data, from the terminal, is treated as follows:
82530 Full duplex, dual channel serial communications controller capable of working in asynchronous, bit or byte synchronous modes. The 82530 receives commands from the terminal's RS232 or X.21 interface and passes them on to the 80188.
Data from the terminal passes via the 82530 to RAM via one of the 80188 DMA channels. The 80188 fetches the data from RAM, depacketizes and packetizes it before sending it back to the 82530 where a protective HDLC protocol is added.
80188 After having received the dialing information from the keyboard, the 80188 sets up the call via the 29C53 Dchannel by sending the appropriate CCITT message up the link. • Call setup message generation (CCITT 1.451).
From the 82530 the data reaches the EPLD to be inserted into the B1 or B2 channel on the SLD bus. The 29C53 sends it out over the "S" interface.
• Hayes is a registered trademark of Hayes Microcomputer Products, Inc.
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SLD
P3/4
RS 232 C
300 - 19 200 blt/s
oR X.21 600 - 48 000 blt/s
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Figure 1. Terminal Adaptor
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ISDN PHONE WITH BUILT IN TERMINAL ADAPTOR (TA) Figure 2 shows the concept of an ISDN phone with hookup to standard sync/async terminals. No change at the terminal is required to make it ISDN compatible. The design is based on a 29C53 transceiver for the ISDN connection, a 29C48 combo for the voice connection and an 80188 microprocessor in combination with an 82530 communications controller for the data connection. Benefits of the application are: • Data rates up to 19.2 kb/s using an RS232 interface o~ up to 48 j<.b/susing an X.21 interface. • Compact design and low cost. • Virtually error free transmission.
Link Setup Applies both for speech and dat~ links. The 80188 accepts the command and begins the call setup procedure by communicating the call's destination: to the NT (or CO):This-is achieved by passing call setup messages to a link level protocol, which is passed to the NT over'the physical level (S-bus). The partitioning of the tasks is as follows:
- Error correction (retransmission) - Flow control
EPLD • Interface conversion, serial to/from SLD • B-channel assignment
29C53 • Physical level interface (CCITT 1.430) • Lower portion of the link access procedure: - Zero insertionldeletion - CRC generation and checking - Flag appending and detection • D-channel message buffering The 80188 passes the information for the D-channel messages via the parallel bus into the FIFO's of the 29C53. The NT grants a B-channel (if available) to the TA and ,the channel is now ready for data transfer.
8279 The 8279 keyboard and display controller scans the telephone number pad and supports a small telephone display. Calls are initiated either through the terminal keyboard using an extended Hayes Smart Modem command set or via the telephone number pad.
82530 Full duplex, dual channel serial communications controller capable of working in asynchronous, bit or byte synchronous modes. The 82530 receives commands from the terminal's RS232 or X.21 interface and passes them on to the 80188.
80188 After having received the dialing information from either keyboard, the 80188 sets up the call via the 29C53 D-channel by sending the appropriate message up the link. • Call setup message generation (CCITT 1.451) • Upper portion of link access procedure (CCITT 1.440) handling: - Multiple logic channels - Sequence control
Information Transfer VOICE
The voice transfer is supported by the 29C48 which transmits the voice on either the BI or B2 channel (controlled by the EPLD) into the 29C53 and onward to the S-bus.
DATA An indication is given to the user's terminal via the RS232 or X.21 port that communication may commence. Any subsequent data, from the terminal, is treated as follows: Data from the terminal passes via the 82530 to RAM via one of the 80188 DMA channels. The 80188 fetches the data from RAM, depacketizes and packetizes it before sending it back to the 82530 where a protective HDLC protocol is added. From the 82530, the data reaches the EPLD to be inserted into the BI or B2 channel on the SLD bus. The 29C53 sends it out over the "S" interface.
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Figure 2. ISDN Phone With Built In Terminal Adaptor
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PERSONAL COMPUTER INTERFACE Like the terminal adaptor, the ISDN PC adaptor provides a link to the ISDN network. The ISDN CoProcessor shown in Figure 3 implements the hardware functions required to support the CCITI I-series "S" interface.
29C48 Voice conversion and interface to the four wire handset is performed by this software programmable integrated Codec/filter combo. Designed for ISDN terminal applications it offers programmable gain in transmit and receive direction for user loudness control and adaptation to local network requirements as well as sidetone insertion and tone injection for locally produced feedback signals.
The ISDN Co-Processor is using the 80188 microprocessor in combination with an 82530 serial communications controller for data processing, dual port RAM as interface and buffer to the host bus, the 29C48 Codecl filter for voice support and the 29C53 transceiver for the ISDN connection.
The 29C48 can access either B1 or B2 channel by setting the B Sel pin accordingly.
The ISP188 ISDN Software Package is optimized for this hardware configuration.
29C53
82530
"s" bus transceiver and D channel controller in a single chip. The 29C53 provides the physica1level interface to the "s" bus in accordance to CCITI 1.430 and the lower portion of the link access protocol. Activation, deactivation, zero insertiOn/deletion, CRC generation and checking and flag appending and detection are performed by the 29C53, the higher level portions of LABD are executed on the 80188 and passed on to the 29C53 via the parallel bus into the FIFO's.
Full duplex, dual channel serial communications controller. One of the two channels is attached to either of the B channels and operates at 64 kb/s. The second channel is available to external datacom equipment via an optional serial port, or for connection to the second B channel.
B channel access is via the SLD serial port. Voice signals are directly passed on to the 29C48. Data is extracted and injected by the EPLD (Erasable, Programmable Logic Device) which performs the B channel assignment and the interface conversion to the 82530.
Co-Processor The PC adaptor is an intelligent communications subsystem designed to function as a slave processor board in the PC. This relieves the host processor of much of the communications function.
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DUAL PORT RAIl
80188
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270247-4
Figure 3. Personal Computer Interface 5-97
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FULL FEATURE ISDN LINE CARD
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LINE CARD CONTROLLER CS INT
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I PACKET NETWORK
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PCS4 UCS LCS INT3 PCSO.1 PSC2.3
270247-3
Figure 4. Full Feature ISDN Line Card The addition of ISDN line cards to a PABX provides the user with access to the ISDN network. While the analog line card provides access for standard telephone as well as for modems, ISDN terminal adaptors, terminals and phones are connected to the ISDN line card via a 4 wire'S' loop. The described application provides all functions to separate voice and switched data (Bchannels) from signaling and packetized data (D-channe1).
4. The 80188 determines whether the data is for signaling (S-packet) or is a message to be sent out over the packet (P-packet) switched network. Signaling information can be processed locally or sent via the linecard controller. If the data is of "P" type, meant for the packet switched network, it is DMA'd into the 82530 serial communications controller which performs the nee.essary HDLC transmission, again without any CPU involvement.
The 29C53 and 80188 together handle the processing of D-channel protocols and messages as follows:
5. The 80188 software is responsible for sending out acknowledgements for received messages from the 29C53's D-channe1 and can thus support large window sizes.
1. The 29C53 executes all bit level HDLC processing, puts the "raw" messages into its FIFO and raises the interrupt signal. 2. A special status register in the 29C53s allows the 80188, through a single status read operation, to determine which of the 29C53s is requiring interrupt servicing, i.e. has D-channel messages(s) in its FIFO.
B-channel information is directly passed from the "S" loop over the 29C53 and line card controller to the switch backplane.
3. The 80188 accesses the FIFO concerned and the data is transferred to RAM.
For transmission in the opposite direction, the procedure is equivalent to the one described above.
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OTHER AVAILABLE TELECOM LITERATURE Order Number
Title
29C53 Reference Manual
270151-001
29C53 Line Card Evaluation Kit (LEK) Manual 29C53 Terminal Evaluation Kit (TEK) Manual ISP188 ISDN Software Package for the 80188 IDK29C53 ISDN Development Kit for 29C53 PC53 ISDN Board
5-99
290149-001
